1. Field of the Invention
The present invention relates to a refrigerant transporting hose and particularly to such hoses suitable for providing piping for car coolers, air conditioners and the like which are employed in automotive vehicles.
2. Related Art Statement
Referring to FIG. 2, there is shown a known hose for transporting or conducting a refrigerant such as Freon (fluorohydrocarbon). The hose has a three-laminated or layered structure consisting of an inner and an outer rubber tube 101, 103 and a reinforcing fiber layer 102 interposed between the inner and outer tubes 101, 103. The inner rubber tube 101 is formed of acrylonitrile-butadiene rubber (NBR), chlorosulfonated polyethylene rubber (CSR) or the like, the reinforcing fiber layer 102 is formed of polyester fiber, vinylon fiber (polyvinyl alcohol synthetic fiber) or the like, and the outer rubber tube 103 is formed of ethylene propylene diene rubber (EPDM), chloroprene rubber (CR) or the like. Reference numerals 115 designate spiking holes which are formed through the outer rubber tube 103 so as to communicate the reinforcing fiber layer 102 with ambient atmosphere outside the hose. The spiking holes 115 serve to relieve a portion of the refrigerant (Freon) which has permeated the inner rubber tube 101, into the ambient atmosphere, thereby preventing the hose from being swollen due to the refrigerant otherwise trapped between the intermediate fiber layer 102 and the inner and/or outer rubber tubes 101, 103. Thus, the hose is free from the problem of separation or peeling of each of the three laminates (one layer and two tubes) from the others due to the trapped refrigerant. Being formed of rubber material except for the reinforcing fiber layer 102, the hose has a high flexibility. Accordingly, the hose can be handled with ease, for example to provide rubber piping. Also, the rubber hose has an excellent seal characteristic, so that the hose can be connected with high gas tightness to a nipple or other joints. Rubber materials, however, have a comparatively high gas permeability, that is, a comparatively low resistance to gas permeation therethrough. Therefore, the rubber hose suffers from the problem of leakage of the refrigerant gas conveyed therethrough (especially where Freon whose molecular weight is comparatively low is used as the refrigerant).
Referring to FIG. 3, there is shown another known refrigerant transporting hose including an innermost resin layer 204 formed of a polyamide resin, such as nylon 6, which has a high resistance to gas permeation. The innermost resin layer 204 and a rubber layer 205 formed of a rubber material such as NBR and located outside the resin layer 204 correspond to the inner rubber tube 101 of the hose of FIG. 2. The hose further includes a reinforcing fiber layer 202 formed on the outer surface of the rubber layer 205 and an outer rubber tube 203 formed on the outer surface of the reinforcing fiber layer 202. Reference numerals 215 designate spiking holes similar to those 115 of the hose of FIG. 2. Having the innermost resin layer 204 formed of nylon 6 or other polyamide resins that have a high resistance to gas permeation, the hose does not allow leakage of the refrigerant even if Freon whose molecular weight is comparatively low is used as the refrigerant. However, the hose suffers from a comparatively low flexibility due to the rigidity of the innermost resin layer 204. Accordingly, it is not easy to handle the hose, for example to provide rubber piping for a refrigerant-using device or apparatus. Furthermore, the hose suffers from the problem that the polyamide resin layer 204 is deteriorated or damaged due to metallic ions and/or metallic salts developed from metallic piping or other metallic parts.
As is apparent from the foregoing, none of the conventional refrigerant transporting hoses are satisfactory in quality.